A method and a device for controlling an internal combustion engine in which an actual value is determined based on a lambda value and compared with a setpoint value is described, for example, in German Patent No. DE 102 21 376. A correction value for a controlled variable, in particular for an air mass signal and/or a fuel mass signal, is determined based on the comparison of the actual value and the setpoint value and is stored.
When controlling internal combustion engines, components used for controlling the internal combustion engine must be monitored for errors. Errors in which increased emissions or increased power of the internal combustion engine occur due to an increased supply of fuel are regarded as particularly problematic.
According to the present invention, an error is detected based on the comparison of two correction values. In particular, an old, stored correction value is compared with a new correction value. According to the present invention, it was recognized that specific errors occur suddenly and thus result in an abrupt change of the correction value.
Therefore, it is particularly advantageous if an error is detected when the correction value changes by more than one threshold value since a previous determination. This means in particular that a check is performed to determine whether the correction value has changed by more than one threshold value since it was last determined. In this way, it is possible to reliably detect an abrupt change of the correction value. It is advantageous in particular if a timing condition is considered in this process, i.e., the threshold value is specified as a function of the time since the last determination or the change of the correction value is weighted with time. Only the time during which the internal combustion engine is operated is considered.
Such a procedure makes it possible in particular to detect unauthorized interventions in the control which result in increased power of an internal combustion engine due to an increased quantity of fuel injected.
Errors relating to the injection components, e.g., the injectors, are detected particularly reliably. It is particularly advantageous if emergency operation is initiated when an error is detected. This may be implemented, for example, by operating the internal combustion engine at significantly reduced power. It is particularly advantageous if the correction values are documented when an error is detected. This makes it possible to detect and document an unauthorized intervention in the control.